I am yet to read any of these, but I am going to add few of mine here as well:
Metalo really leans into the POA! vibe of Sirius, where he is so compelling and frightening, and the atmosphere is just filled with him. It works wonderfully for this ship - and it was my first time reading them as teenagers. Also, this exchange is really funny:
“What a surprise. A blood traitor sticking up for another,” Regulus drawls, after some seconds, eyes moving between his brother and Potter, filled with anger. “You know how protective he is over his boyfriend, Mulciber.”
“You little shit.” Black steps forward, and if Regulus can look down at most people his age and many older than him, he can’t do that with his brother.
Regulus opens his mouth, but just then Slughorn comes out of the classroom. “Everything alright?”
They all go off at once.
Lily says Regulus is insulting people, Avery complains Lily is abusing her Head Girl position to take points for no reason and that Potter threatened to curse him. Potter says Avery is a liar, and they all talk over each other.
Watch the warnings for this one. This one particularly required me to be in a certain mindspace to read it..but it was beautifully written, and an extremely visceral read. It teases out every dynamic and nuance in all the hate-smut.
Violent, fragile and everything in between. Again, mind the warnings. (this work also has a sequel which I havent read yet)
An alternate take on the kitchen scene in OOTP, and in first person!!
Canon-divergence from POA. I've had much fun reading this domestic, almost tender piece.
There is more for sure, but this is off the top of my head.